Acute infection patients have more partners

Higher chance of infection spreading in networks

New research suggests that patients with acute HIV infection have a significantly larger number of partners than what has been reported, historically, by HIV patients with non-acute infection.1

"The research suggests people with acute infection are more likely to be in sexual networks that are a little more complex or are more likely to have more partnerships at that time than other infected people," says Christopher D. Pilcher, MD, an assistant professor in the school of medicine at the University of North Carolina at Chapel Hill.

"That may lead to a higher likelihood of infection spreading in a population," Pilcher says. Pilcher was involved with several studies involving the North Carolina Department of Health and Human Services Screening & Tracing Active Transmission (STAT) program, which were presented at the 13th Conference on Retroviruses and Opportunistic Infections (CROI), held in Denver, Feb. 5-8.

The sexual network finding was part of an investigation that included tracing individuals who were identified as having acute infections, Pilcher says.

All 135 public HIV-testing sites in North Carolina have used a combined HIV antibody and RNA testing algorithm through the State Laboratory of Public Health, as part of the STAT program, which has become well-known for its success in identifying acute HIV infection cases.1

Since the program began Nov. 1, 2002, through Oct. 31, 2004, there were 227,566 public tests conducted, and of these 1,123 were newly antibody positive, and another 44 were true acute infections. Investigators interviewed 41 of the people with acute infections.1

"Disease intervention specialists from North Carolina were remarkably successful at reaching these patients very quickly, as well as reaching their partners and counseling exposed partners that they might be at risk for HIV infection," Pilcher says.

The disease intervention specialists followed the partners, providing HIV testing, counseling, and, sometimes, clinical evaluation, for up to two years, Pilcher says.

They found that of 12 partners, who were completely evaluated and had documentation of previous HIV negative status, three were antibody positive initially and another three were RNA positive, indicating an acute infection, Pilcher says.

"So half were newly HIV positive, and at least three of them we’re certain were acutely infected as a result of their exposure to their HIV infected partners," he says. "So this is a very real world kind of reinforcement of the value of following up on partners of newly diagnosed HIV patients."

Among the acute infection cases were 16 women, and five of the women were pregnant at the time of their testing, Pilcher says.

During this same time period there were six infants born with HIV infection in North Carolina; and in three of those cases the mothers had been tested and were negative early in their pregnancies, so they had seroconverted during their pregnancy, Pilcher notes. "So we managed to detect and avert five additional acute infections during pregnancy, just through the testing program," Pilcher says.

Researchers concluded that standard antibody tests miss at least 4% of the HIV-infected pregnant women in the state, and so the use of STAT could significantly improve the performance.2

"We should not only repeat HIV testing at the time of labor for women who are tested and negative, but we should also include the use of nucleic acid testing for any HIV testing during pregnancy, because it seems clear that acute infection occurring during pregnancy is responsible for a large proportion of residual mother to child transmission in North Carolina," Pilcher says.

Another study related to the STAT program looked at its cost effectiveness and found that the cost per quality-adjusted life-years (QALY) was $4,345, which is well below the cost-effectiveness threshold of $50,000.3

Investigators concluded that screening negative samples for acute HIV infection using the STAT approach should be considered wherever there is a 0.55% positive HIV test rate and where notification and follow-up are possible.3

The study tried to quantify what would be the direct results of detection of acute HIV infections that would otherwise be missed over a one year period of testing, Pilcher explains.

"The study did not account for the downstream impact of transmitting infection to many individuals," Pilcher notes. "It looked at what would happen in 12 months of time if it detected the exact number of cases that we detected and averted exactly the number of cases that we believe we averted."

Since only one-third of babies are infected with HIV naturally from their HIV infected mothers without intervention, the discovery of five acutely infected pregnant women would have saved, conservatively, one or two babies from HIV infection, Pilcher says. "So by plugging in all of the real numbers and knowing exactly what the outcomes were and then estimated from the published literature what the costs of an HIV infection are over an individual’s lifetime, the study came up with the cost of the additional testing per quality adjusted life year," Pilcher says.

"For cost effectiveness modeling we used extraordinarily conservative assumptions about what the impact was of telling partners and patients and the impact of risk reduction counseling for acutely infected patients and their partners," he says. "We assumed there would be only a 50% reduction in risk after knowing their status."

This means there would be about ½ to 1 adult case averted each year, Pilcher says.

"We believe in reality it is much higher, but we felt in terms of a cost effectiveness analysis that it was important to use the most conservative model possible," Pilcher says.

References

  1. Pilcher CD, Foust E, Ashby R, et al. Sexual transmission risk and rapid health intervention in acute HIV infection. Presented at the 13th Conference on Retroviruses and Opportunistic Infections, held Feb. 5-8, 2006, in Denver, CO. Abstract: 371.
  2. Patterson K, Leone P, Fiscus S, et al. Detection of acute HIV infection in pregnant women. Presented at the 13th Conference on Retroviruses and Opportunistic Infections, held Feb. 5-8, 2006, in Denver, CO. Abstract: 370.
  3. Simpson K, Biddle A, Leone P, et al. Presented at the 13th Conference on Retroviruses and Opportunistic Infections, held Feb. 5-8, 2006, in Denver, CO. Abstract: 374.